I have noticed this a lot in the past few weeks (or couple of months), compared to what it was an year ago.
1_ There is some sort of lag in the editor, no matter what the internet speed is. This slowness is subtle, but is something you would notice, if you had been using it regularly in the past 2 years.
2_ The time it takes between you hitting "Run" and actually getting the result also slows down sometimes, irrespective of the complexity of the algorithm:). After a screen refresh, it gets better.

I am still not sure, if its the internet speed. But I have checked my speed, do not see the lag on other sites.